The present invention relates to a cage for supporting an optical transceiver on a host circuit board, and in particular to a cage providing electromagnetic interference shielding, as well as facilitating increased thermal dissipation.
Transceiver cages provide a guide for xe2x80x9chot pluggingxe2x80x9d an electrical connector of an optical transceiver module into a mating electrical connector on a host circuit board. Conventional cages for the GBIC transceiver product, such as the one disclosed in U.S. Pat. No. 5,767,999 issued Jun. 16, 1998 to Vixel Corporation, and generally indicated at 1 in FIG. 1, include a plastic frame 2 with an elongated guide rail 3 for engaging a channel formed in the side of the GBIC transceiver housing to guide the transceiver into contact with the host connector. Holes 4 are provided in the frame 2 for receiving a locking detent resiliently biased outwardly from the side of the transceiver housing. A door 6, pivotally mounted on the frame 2, is resiliently biased shut to prevent dust or any other foreign matter from entering the cage 1 through the opening 7. EMI clips 8 are mounted on the frame 2 proximate the opening 7, so that spring fingers 9 extend therein. The plastic GBIC cage 1 has a completely open top, which enables the circulation of air for heat dissipation, but provides no EMI protection nor the ability to mount any additional thermally conductive surfaces for added heat dissipation. Pluggable small form factor (SFP) cages 10, such as the ones disclosed in U.S. Pat. No. 6,419,523 issued Jul. 16, 2002 to Hon Hai Precision Ind. Co. and illustrated in FIG. 2, completely surround the transceiver module except for a few holes 12 in the top 11, thereby eliminating the need for a guide rail, while providing good EMI protection. A resilient flange 13 is provided for locking the transceiver module into the cage 10. The top 11, the base 14 and the sides 15 are provided with spring fingers 16 for grounding the cage 10 to the host device chassis. Pins 17 are provide for securing the cage 10 to the host circuit board. Unfortunately, the amount of heat dissipation is greatly reduced, as air flow over the transceiver module is limited. Moreover, since the transceiver module is completely enclosed, no additional thermally conductive surfaces can be mounted thereto for added heat dissipation.
Recently developed higher power transceivers, e.g. transmitting at 10 Gb/s, require both EMI protection and the ability to dissipate larger amounts of heat. Therefore, the cages developed for the new transceivers need to provide both good EMI shielding and facilitate the dissipation of heat.
An object of the present invention is to overcome the shortcomings of the prior art by providing an optical transceiver cage with a simple guiding feature, good EMI protection, and with the ability to dissipate excess heat.
Accordingly, the present invention relates to a metal cage mountable on a circuit board of a grounded host device for receiving an optical transceiver therein comprising:
a front shroud, having a base, two sidewalls and a top, defining an opening for receiving the optical transceiver during installation, and for surrounding a front portion of the optical transceiver during use;
a rear shroud, including: an open bottom, for receiving an electrical connector mounted on the circuit board; two sidewalls; and a top, the two sidewalls and the top for surrounding a rear portion of the optical transceiver during use;
a middle section extending between the front and rear shrouds having a base, two sidewalls and a substantially open top; and
at least one cross bar extending from the top of the front shroud to the top of the rear shroud for guiding the optical transceiver during installation.